Although a bias term is adopted by the Saab transform to address the
sign confusion problem in [1]}, this term is
removed in the later Saab transform implementation for the following
reason. The sign confusion problem actually only exists in neural
network training because of the use of backpropagation optimization. In
this context, one determines both the embeddings from the previous layer
and the filter weights of the current layer simultaneously based on the
desired output. In contrast, the input to the current layer is already
given in the feedforward design, one need to determine filter weights
first based on the statistics of the current input and then compute the
filter responses. As a result, there is no sign confusion problem in the
FF-CNN.
